A magnetic head includes a first electrode layer, a first ferromagnetic electrode pair that is electrically connected to the first electrode layer, and a second ferromagnetic electrode pair that intersects with a current which flows between the first ferromagnetic electrode pairs and is electrically connected with the first electrode layer. The current is allowed to flow between the first ferromagnetic electrode pair through the first electrode layer to accumulate spin electrons in the first electrode layer. A direction of magnetization of the fourth ferromagnetic electrode layer changes upon application of an external magnetic field. The second ferromagnetic electrode pair is so arranged as to intersect with the current that flows between the first ferromagnetic electrode pair, to increase a rate of change in the output signal of the in-plane spin accumulation effect.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A magnetic head, comprising: a first electrode layer; a first ferromagnetic electrode pair having a first ferromagnetic electrode layer that is stacked on one end of the first electrode layer through a first insulating layer, and a second ferromagnetic electrode layer that is stacked on the other end of the first electrode layer through a second insulating layer; and a second ferromagnetic electrode pair having a third ferromagnetic electrode layer that is stacked on one end of the first electrode layer through a third insulating layer, and a fourth ferromagnetic electrode layer that is stacked on one end of the first electrode layer through a fourth insulating layer; wherein the second ferromagnetic electrode pair intersects with a current that flows between the first ferromagnetic electrode pair; wherein the current is allowed to flow between the first ferromagnetic electrode pair through the first electrode layer to accumulate spin electrons in the first electrode layer; wherein a direction of magnetization of the fourth ferromagnetic electrode layer changes upon application of an external magnetic field; and wherein a coercive force of the fourth ferromagnetic electrode layer is smaller than a coercive force of the first and third ferromagnetic electrode layers.
2. A magnetic head, comprising: a first electrode layer; a first ferromagnetic electrode pair having a first ferromagnetic electrode layer that is stacked on one end of the first electrode layer through a first insulating layer, and a second ferromagnetic electrode layer that is stacked on the other end of the first electrode layer through a second insulating layer; and a second ferromagnetic electrode pair having a third ferromagnetic electrode layer that is stacked through a third insulating layer on one end of the first electrode layer, which is different from portions of the first electrode layer which are electrically connected with the first and second ferromagnetic electrode layers, and a fourth ferromagnetic electrode layer that is stacked through a fourth insulating layer on the other end of the first electrode layer, which is electrically connected with the third ferromagnetic electrode layer; wherein a current is allowed to flow between the first ferromagnetic electrode pair through the first electrode layer to accumulate spin electrons in the first electrode layer; wherein a direction of magnetization of the fourth ferromagnetic electrode layer changes upon application of an external magnetic field; and wherein a coercive force of the fourth ferromagnetic electrode layer is smaller than a coercive force of the first and third ferromagnetic electrode layers.
3. The magnetic head as claimed in claim 1 or 2 , wherein the first ferromagnetic electrode pair is connected to a constant current circuit as a current terminal, a direction of the applied magnetic field is not substantially identical with a direction along which the current flows in the first electrode layer through the ferromagnetic electrode pair.
4. The magnetic head as claimed in claim 1 or 2 , wherein in an arrangement of the ferromagnetic electrode layers of the second ferromagnetic electrode pair on the first electrode layer, distances between substantially center portions of the respective surfaces where the third and fourth ferromagnetic electrode layers are in contact with the first electrode layer and a substantially center portion of a surface where the first ferromagnetic electrode layer is in contact with the first electrode layer are substantially identical with each other.
5. The magnetic head as claimed in claim 1 or 2 , wherein in an arrangement of the ferromagnetic electrode layer of the second ferromagnetic electrode pair on the first electrode layer, the respective surfaces where the four ferromagnetic electrode layers and the first electrode layer are arranged on the same surface of the first ferromagnetic electrode layer, the fourth ferromagnetic electrode layer are in contact with films of upper and lower shields, respectively, and the upper and lower shields are isolated from the first electrode layer and the ferromagnetic electrode layers with insulating layers except for the contact portions of the fourth ferromagnetic electrode layer with the films of the upper and lower shields.
6. The magnetic head as claimed in claim 1 or 2 , wherein in an arrangement of the ferromagnetic electrode layers of the second ferromagnetic electrode pair on the first electrode layer, the respective surfaces where the four ferromagnetic electrode layers are in contact with the first electrode layer have a structure in which the fourth ferromagnetic electrode layer is arranged on one surface of the first ferromagnetic electrode layer, the second and third ferromagnetic electrode layers are arranged on a rear surface of the first ferromagnetic electrode layer, the fourth ferromagnetic electrode layer is in contact with one of the films of the upper and lower shields, and the second ferromagnetic electrode layer is arranged on the same surface of the first ferromagnetic electrode layer as the fourth ferromagnetic electrode layer or the rear surface of the first ferromagnetic electrode layer, and the upper and lower shields are isolated from the first electrode layer and the ferromagnetic electrode layers with insulating layers except for the contact portions.
7. The magnetic head as claimed in claim 1 or 2 , wherein all of the first to third ferromagnetic electrode layers arranged on the first electrode layer, or at least the first and third ferromagnetic electrode layers have entire surfaces or at least the contact surface portions which are in contact with the first electrode layer are in direct contact with a film of an anti-ferromagnetic material, or in contact with the film of the anti-ferromagnetic material through a ferromagnetic metal film.
8. The magnetic head as claimed in claim 1 or 2 , wherein the fourth ferromagnetic electrode layer disposed on the first electrode layer has a length in a direction orthogonal to a medium surface which is longer than a length in a direction parallel with the medium surface.
9. The magnetic head as claimed in claim 1 or 2 , wherein in the fourth ferromagnetic electrode layer disposed on the first electrode layer, a magnetic domain structure is aligned by one of a structure in which permanent magnet layers are disposed on both ends of the fourth ferromagnetic electrode layer through insulating layers, and magnetization of the fourth ferromagnetic electrode layer is fixed by a leakage magnetic flux from the both ends of the fourth ferromagnetic electrode layer, and a structure in which a nonmagnetic film is disposed on the other main surface side of the fourth ferromagnetic electrode layer, a permanent magnet film or a multiplayer film including an anti-ferromagnetic film and a magnetic film is in contact with the other main surface side of the fourth ferromagnetic electrode layer, and magnetization of the fourth ferromagnetic electrode layer is fixed by a magnetic flux from the both ends of the fourth ferromagnetic electrode layer.
10. The magnetic head as claimed in claim 1 or 2 , wherein a part of the fourth ferromagnetic electrode layer disposed on the first electrode layer is exposed to a surface that faces a medium surface.
11. The magnetic head as claimed in claim 1 or 2 , wherein a part of the fourth ferromagnetic electrode layer disposed on the first electrode layer is not exposed to a surface that faces a medium surface, and disposed through a protective film.
12. The magnetic head as claimed in claim 1 or 2 , wherein the first electrode layer is made of good conductor metal and compound of Al, Pt, Au, Ag, Pd Cu or TiN, or semiconductor material mainly containing Si, GaAs or As, or Sb.
13. The magnetic head as claimed in claim 1 or 2 , each of the first to fourth ferromagnetic electrode layers is formed of a single layer film or a composite multiplayer film containing: ferromagnetic metal of Co, Fe or Ni, or ferromagnetic alloy mainly containing Co, Fe or Ni; an oxide having a structure of AB 2 O 4 where A is oxide containing at least one of Fe, Co and Zn, and B is oxide containing one of Fe, Co, Ni, Mn and Zn; a compound of CrO 2 , CrAs, CrSb or ZnO added with at least one component of Fe, Co, Ni, Cr and Mn which are transition metal; a compound of GaN added with Mn; or a C 2 D x E 1-x F type Heusler alloy where C is at least one of Co, Cu and Ni, D and E are one of Mn, Fe and Cr, respectively, and F contains at least one component of Al, Sb, Ge, Si, Ga and Sn.
14. The magnetic head as claimed in claim 1 or 2 , wherein each of the first to fourth insulating layers is formed of a single layer film or a composite multi-layer film which mainly contains Al 2 O 3 , AIN, HfO 2 , SrTiO 3 , Cr 2 , O 3 , ZrO 2 , SiO 2 , or MgO.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
September 1, 2004
August 7, 2007
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